The invention relates to a resilient harrow tine of S-like shape and comprising an upper, resilient hoop portion bent substantially to form a circle and having a cross-section, the circumscribed rectangle of which has a ratio between the width and the height of about 3, the cross-sectional long side facing outwards in the resilient hoop portion being substantially rectilinear.
A harrow tine of said type is generally produced from a rolled steel bar of rectangular or substantially rectangular cross-section.
Such a harrow tine blank is for instance disclosed in United Kingdom patent specification No. 1,178,370 according to which the cross-section is slightly convex at one of its long sides. By bending said blank into S-shape the cross-section assumes a practically symmetrical shape and the neutral axis of stress becomes consequently coincident with the longitudinal centre line of the cross-section.
When in operation, the resilient hoop portion of the tine is tensioned at its outwardly facing side and for this reason much care is taken in dimensioning and production to avoiding stress concentrations at this side. In known harrow tines this is achieved, inter alia by providing suitably smooth transitions between the outwardly facing side and the short sides and by ball hammering the surfaces whether the cross-section of the blank is absolutely rectangular or possibly slightly curved as stated above.
As a consequence of the above mentioned measures, harrow tines manufactured according to the prior technqiue may fulfil the conditions necessary for the working ability of the tine with a view to strength, resilience and stability.
By thorough analysis of the stress to which the harrow tine is subjected when in operation, for instance by means of strain gauges and by estimating the stress distribution over the cross-section, it has been established, however, that the material is not fully utilized. This implies that known harrow tines require more material than strictly necessary to obtain the desired strength, and from this recognition it is an aim of the invention to provide a harrow tine with an optimum proportion between strength and material consumption.